1. Field of the Invention
The invention is in the field of magnetic materials for use at transmission carrier frequencies.
2. Brief Description of the Prior Art
The temperature variation of the magnetic permeability of materials used in communication systems has been of continuing concern to the designer of devices such as frequency selection filters. If metallic magnetic materials are to be used at high frequencies, some method of reducing eddy current losses is usually required. One widely used class of materials consists of fine particles of the magnetic material which are coated with an insulating material and compressed to form the desired magnetic body. Two common materials used in this fashion are carbonyl iron powders and pulverized permalloy powders. In order to control the temperature variation of the magnetic properties of powder cores, trial and error mixture of powders exhibiting different temperature variation has been used. For example, permalloy of different alloy compositions have been incorporated in temperature compensated powder cores (Metal Progress, 54 (1948) Page 710-711). The objective there, was to minimize the temperature variation of the permeability of the magnetic body over the temperature range of interest. The usual procedure has been to form a series of test bodies incorporating the constituent powders in various proportions until the mixture producing the desired properties is found.